Apparatus for transmitting a signal below a current transmit power in a network

ABSTRACT

A transmitter includes a detection element to determine when a current power requirement of a communication link is less than the standard transmit power. The current power requirement may be determined by a current operation condition of the communication link, for instance. The transmit power of the transmitter may be set to be less than the standard power in any of a variety of ways. For example, a center tap voltage of the transmitter may be reduced. In another example, a class of operation of the transmitter may be changed. In yet another example, the transmitter may include a current mirror having a plurality of diode-connected transistors coupled in parallel, thereby reducing the current at output terminals of the transmitter. Reducing the current at the output terminals decreases the output power of the transmitter, which may reduce the power consumed by the transmitter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/099,031, filed May 2, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/620,215, filed Nov. 17, 2009, which is acontinuation of U.S. patent application Ser. No. 11/220,623, filed Sep.8, 2005, which claims priority to U.S. Provisional Application No.60/608,146, filed Sep. 9, 2004, all of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to networks, and morespecifically to setting transmitter power in a network.

2. Background

Devices in a network generally include transmitters to transmitinformation via an electrically conductive medium, such as a twistedwire pair, a coaxial cable, a fiber optic cable, etc. For instance, atransmitter in a first device can transmit information to a receiver ina second device, and a transmitter in the second device can transmitinformation to a receiver in the first device. Devices that areconnected in a network are often referred to as link partners. Thetransmit and receive functions of a link partner are often combinedusing a transceiver.

Ethernet is a type of network having link partners that are oftenconnected via twisted pair cable. Components, such as transmitters andreceivers, in an Ethernet system may be configured to operate at any ofa variety of speeds. The speed of transmission between link partners isoften limited to the capability of the slower link partner. A componentmay be capable of operating at 10 megabits per second (Mbps) (referredto as 10 Base-T), 100 Mbps (referred to as 100 Base-T), and/or 1000 Mbps(referred to as 1000 Base-T), to provide some examples.

Conventional transmitters in a network transmit signals at a standardtransmit power that is defined by a communication standard. For example,conventional Ethernet transmitters operate at a standard transmit powerdefined by a standard associated with. Ethernet, regardless of the powerrequirements of an application. The power consumption of suchconventional transmitters does not decrease for applications having alower transmit power requirement.

What is needed, then, is an apparatus and method for reducingtransmitter power for applications that do not require the standarddefined level of transmit power.

BRIEF SUMMARY OF THE INVENTION

An apparatus and method for setting a transmit power at less than astandard transmit power is provided. A communication standard definesthe standard transmit power. A transmitter includes a detection elementto detect whether the current transmit power can be reduced below thestandard transmit power. Detection by the detection element may be basedon an operating condition of a communication link and/or thetransmitter. The operating condition may be based on a length of acommunication link, an attenuation characteristic of the communicationlink, an environmental condition of the communication link, or a speedof transmission associated with the communication standard, to providesome examples. The detection element may detect that the standardtransmit power is unnecessary based on a 1000 base-T protocol, forexample.

If the standard transmit power is unnecessary, any of a variety of meansmay be used to set a transmitter power of the transmitter to be lessthan the standard transmit power. According to a first embodiment, acenter tap voltage of the transmitter is reduced. In a secondembodiment, a class of operation of the transmitter is changed.According to a third embodiment, the transmitter includes a currentmirror having a plurality of diode-connected transistors coupled inparallel, thereby reducing the current at output terminals of thetransmitter. Reducing the current reduces the output power of thetransmitter, which may reduce the power consumed by the transmitter.Setting the transmit power may reduce the current drawn by thetransmitter. The transmitter value may be set at any value less than thestandard transmit power. For example, the transmit power may be set at20%, 50%, or any other percentage of the standard transmit power. Thetransmit power may be successively reduced, based on a series ofdetections performed by the detection element.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate embodiments of the present inventionand, together with the description, further serve to explain theprinciples of the invention and to enable a person skilled in thepertinent art(s) to make and use the invention.

FIG. 1 illustrates an Ethernet transceiver according to embodiments ofthe present invention.

FIG. 2 is an example schematic representation of the transmitter of theEthernet transceiver shown in FIG. 1 according to an embodiment of thepresent invention.

FIG. 3 shows the transmitter of FIG. 2 having diode-connectedtransistors that are capable of being connected in parallel according toan embodiment of the present invention.

FIG. 4 shows the transmitter of FIG. 2 having diode-connectedtransistors that are capable of being connected in parallel according toanother embodiment of the present invention.

FIG. 5 illustrates a flowchart of a method of operating a transmitter inaccordance with an embodiment of the present invention.

FIG. 6 illustrates a flowchart of a method of operating a transmitter inaccordance with another embodiment of the present invention.

FIG. 7 illustrates a flowchart of a method of operating a transmitter inaccordance with yet another embodiment of the present invention.

In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the leftmost digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

DETAILED DESCRIPTION OF THE INVENTION

Although the embodiments of the invention described herein referspecifically, and by way of example, to Ethernet systems, includingEthernet transmitters, it will be readily apparent to persons skilled inthe relevant art(s) that the invention is equally applicable to othernetworks and systems, including but not limited toserializer/deserializer (SerDes) systems, optical systems, cablesystems, digital subscriber line (DSL) systems, and/or any combinationthereof An Ethernet transmitter can be an Ethernet transceiver, forexample. It will also be readily apparent to persons skilled in therelevant art(s) that the invention is applicable to any network orsystem requiring a reduced transmitter power.

This specification discloses one or more embodiments that incorporatethe features of this invention. The embodiment(s) described, andreferences in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment(s) describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Furthermore, when a particularfeature, structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

I. Introduction

Link partners in a network are connected via a link. The link may be anyof a variety of transmission mediums, including but not limited to atwisted wire pair, a coaxial cable, a fiber optic cable, or anycombination thereof. Link partners in an Ethernet system are oftenconnected via twisted wire pairs. 10 Base-T and 100 Base-T Ethernetsystems utilize two twisted wire pairs. The first pair is unidirectionaltransmit and the second pair is unidirectional receive. Thus, atransceiver in a 10 Base-T or 100 Base-T Ethernet system needs only onetransmitter. 1000 Base-T, on the other hand, uses four twisted wirepairs, and each pair in a 1000 Base-T Ethernet system supportsbidirectional transmit and receive signaling. Thus, a transceiver in a1000 Base-T Ethernet system needs four transmitters. Consequently, 1000Base-T transceivers have a higher power consumption than 10 Base-T or100 Base-T transceivers.

At a standard transmit power, a 1000 Base-T transceiver having fourClass A transmitters (including active hybrid) consumes 440 mW from a2.5 V center tap voltage. At a standard transmit power, 10 Base-T and100 Base-T Class A transceivers consume 250 mW and 100 mW, respectively,from a 2.5 V center tap voltage. A center tap voltage of 2.5 V isprovided for illustrative purpose only. The center tap voltage may beany reasonable value.

The standard transmit power is not necessary for all applications. Forexample, a transmit power that is less than the standard transmit powermay be sufficient for applications utilizing short cable lengths and/orlow attenuation cable. Short cable lengths may be found in backplaneapplications, a conference room connection to a laptop computer, or aconnection between an Internet phone and a laptop computer, to providesome examples.

II. Transmitter Power Setting Embodiments

FIG. 1 illustrates an Ethernet transceiver 100 according to embodimentsof the present invention. Ethernet transceiver 100 includes inputterminals 102, output terminals 104, a center tap voltage 106, andtransmitter 108. Ethernet transceiver 100 may be a link partner in anEthernet network, receiving signals at input terminals 102 andtransmitting signals at output terminals 104. Ethernet transceiver 100may support 10-Base-T, 100-Base-T, 1000 Base-T, another Ethernetstandard, a non-Ethernet communication standard, or any combinationthereof.

In FIG. 1, transmitter 108 transmits an output signal at outputterminals 104 based on data 101. The voltage of the output signal (i.e.,the voltage across output terminals 104) may be based on center tapvoltage 106. For example, varying center tap voltage 106 may vary thedirect current (DC) component of the output voltage, which may bereferred to as the “launch voltage” of transceiver 100. The outputcurrent is based on the configuration of transmitter 108.

FIG. 2 is an example schematic representation of transmitter 108, shownin FIG. 1, according to an embodiment of the present invention. In FIG.2, transmitter 108 includes first inputs 202 a, second inputs 202 b, acurrent mirror 204, a bias source 206, a resistor 208, an active hybrid210, and differential output 104. A communication link 214, such as atwisted wire pair, is coupled to transmitter 108 via transformer 212.Transformer 212 provides a magnetic interface between transmitter 108and communication link 214.

Referring to FIG. 2, bias source 206 biases current mirror 204, therebysetting the current I that flows through transistors 218 a and 218 c orthrough transistors 218 b and 218 d. Transistors 218 c and 218 d operateas a differential amplifier with a differential cascode load provided bytransistors 218 a and 218 b. so as to modulate an output signal atdifferential output 104 with data 101. Transistors 218 a and 218 b aretypically biased to saturation at first inputs 202 a. The current Iflows through transistors 218 a and 218 c when transistor 218 c isturned on and transistor 218 d is turned off by data 101. The current Iflows through transistors 218 b and 218 d when transistor 218 d isturned on and transistor 218 c is turned off by data 101. The current Iflows across resistor 208 to provide the output voltage acrossdifferential output terminals 104.

Data 101 may be used to turn on/off transistors 218 c and 218 d, therebymodulating the current I. As shown in FIG. 2, data 101 is provided to agate of transistor 218 c. Data 101 may be inverted to provide data 101′.In FIG. 2, data 101′ is provided to a gate of transistor 218d. Thus,transistor 218 c is turned on when transistor 218 d is turned off, andvice versa. Switching on transistor 218 c causes the current I to flowacross differential output terminals 104 in a first direction. Switchingon transistor 218 d causes the current I to flow across differentialoutput terminals 104 in a second direction that is opposite the firstdirection.

Transmitter 108 may be biased to operate in any class (e.g., Class A,Class B, or Class AB). For example, transmitter 108 may be biased tooperate in Class A by alternately turning on transistors 218 c and 218d,thereby splitting the current I substantially equally across transistor218 a and transistor 218 b. Biasing transmitter 108 in this mannerprovides an output differential voltage of approximately 0 V. In anotherexample, transmitter may be biased to operate in Class B by turning offboth of transistors 218 a-b, thereby providing an output differentialvoltage of approximately 0 V. The example biasing schemes describedabove are provided for illustrative purposes and are not intended tolimit the scope of the present invention. Class A, B, or AB operationmay be achieved in any of a variety of ways and using any of a varietyof biasing schemes. The output differential voltage need not necessarilybe approximately 0 V. Transmitter 108 may be biased to have anyreasonable output differential voltage.

Active hybrid 210 distinguishes the output signal from an input signalreceived by transmitter 108 and inhibits the output from influencing thereceiver input (not shown). Transmitter 108 need not necessarily includeactive hybrid 210.

In FIG. 2, current mirror 204 includes a transistor 218 e and adiode-connected transistor 216, each of which has a gate, a drain, and asource. The gate and the drain of diode-connected transistor 216 areconnected together. The gates of transistor 218 e and diode-connectedtransistor 216 are connected together. The sources of transistor 218 eand diode-connected transistor 216 are coupled to a ground potential,though the scope of the present invention is not limited in thisrespect. The sources of transistor 218 e and diode-connected transistor216 may be coupled to any voltage potential.

Bias source 206 provides a bias to diode-connected transistor 216 ofcurrent mirror 204. In FIG. 2, the bias provided by bias source 206 is acurrent. The current flowing through diode-connected transistor 216 is“mirrored” at transistor 218 e. In other words, the current I_(bias)flowing through diode-connected transistor 216 and the current I flowingthrough transistor 218 e are the same, assuming that transistor 218 eand diode-connected transistor 216 are the same size. Based on thisassumption, I=I_(bias). However, transistor 218 e and diode-connectedtransistor 216 need not necessarily be the same size. For example, iftransistor 218 e is larger than diode-connected transistor 216, thenI>I_(bias), though the current I increases/decreases as the currentI_(bias) increases/decreases. In another example, if transistor 218 e issmaller than diode-connected transistor 216, then I<I_(bias), though thecurrent I increases/decreases as the current I_(bias)increases/decreases.

The output voltage, which is measured across differential outputterminals 104, is based on the resistance of resistor 208 and thecurrent I. Resistor 208 may be referred to as a source termination.Resistor 208 may be on-chip, meaning that resistor 208 is included in anintegrated circuit (IC) die that includes transmitter 108.Alternatively, resistor 208 may be off-chip, meaning that resistor 208is external to an IC die that includes transmitter 108. In an off-chipconfiguration, resistor 208 may be coupled to the IC die using solderand/or bond wires.

The resistance of resistor 208 and the resistance of a load, such ascommunication link 214, can be approximately the same. For instance,resistor 208 and the load can each have a resistance of 50Ω or 100Ω, toprovide some examples. Resistor 208 and the load can have any suitableresistance, and the resistance of each need not necessarily be the same.

Resistor 208 need not necessarily be a differential resistor, as shownin FIG. 2. In an embodiment, resistor 208 is two single-ended resistors.The first single-ended resistor is coupled between a drain of transistor218 a and a node. The second single-ended resistor is coupled between adrain of transistor 218 b and the node. The node may be connected to asupply voltage, for example.

A communication standard, such as 1000 base-T, may define a standardtransmit power for output signals at output terminals 104. However, notall applications require transmission at the standard transmit power forproper operation.

FIG. 3 shows that transmitter 108 may include a detection element 310 todetermine when a current power requirement is less than the standardtransmit power. The current power requirement may be determined by acurrent operation condition of communication link 214. Example operatingconditions for which the current power requirement may be less than thestandard transmit power include but are not limited to a relativelyshort cable length, a relatively low attenuation characteristic, anenvironmental condition, or transmission speed.

A short cable length may be used in any of a variety of applications,such as a laptop connected to a hub in an office or a conference room,an Internet protocol (IP) telephone connected to a laptop computer, aboard connected to a backplane/chassis of a network, etc. A short cablelength may be defined as a length that is less than a threshold. Thethreshold is determined based on the ability of transmitter 108 totransmit a signal having sufficient power for a receiver to properlyreceive the signal. The threshold may be 1 ft, 1 m, 5 ft, 50 m, 100 m,or any other length. The transmission power of transmitter 108 may beset less than a standard transmit power in response to detection element310 detecting a cable length that does not exceed the threshold.

An attenuation characteristic is defined as an amount of attenuation perunit of length of communication link 214. For instance, communicationlink 214 may have an attenuation characteristic of 1 dB/m, 0.05 dB/ft,etc. A low attenuation cable may be defined as cable having anattenuation characteristic that is less than a threshold. The lowattenuation cable may be specified as cable of a particular type, thoughthe scope of the present invention is not limited in this respect. Forexample, the low attenuation cable may be specified to be category 6cable, category 7 cable, optical cable, etc. The transmission power oftransmitter 108 may be set less than a standard transmit power inresponse to detection element 310 detecting an attenuationcharacteristic that does not exceed the threshold.

An environmental condition may provide a relatively low signal-to-noiseratio (SNR), for example. In this example, the transmission power oftransmitter 108 may be set less than a standard transmit power inresponse to detection element 310 detecting a SNR that does not exceed apredetermined threshold.

A speed of transmission may be defined by a communication standard, suchas 10 base-T, 100 base-T, 1000 base-T, another Ethernet standard, or anon-Ethernet communication standard. The transmission power oftransmitter 108 may be set less than a standard transmit power definedby the communication standard in response to detection element 310detecting a transmission speed associated with the communicationstandard.

Because the power of transmitter 108 is based on the output voltageacross differential output terminals 104 and the current I, the power oftransmitter 108 may be reduced by reducing the output voltage and/or thecurrent I.

According to a first embodiment, the power consumption of transmitter108 is reduced by reducing center tap voltage 106 of transmitter 108.The output voltage (i.e., transmit voltage) of transmitter 108 is basedon the launch voltage of transmitter 108. Center tap voltage 106 is setto accommodate the output voltage swing of transmitter 108. The power oftransmitter 108 is based on the current I and center tap voltage 106.Thus, reducing the output voltage swing at terminals 104 of transmitter108 may allow center tap voltage 106 to be reduced, thereby reducing theoutput power of transmitter 108. Reducing center tap voltage 106 from2.5 V to 1.8 V, peak-to-peak, may reduce the power consumption oftransmitter 108 by approximately 28%, for example. In FIG. 3, center tapvoltage 106 is shown to be 0 V for illustrative purposes. Center tapvoltage 106 may be set to any value.

In a second embodiment, the power consumption of transmitter 108 isreduced by changing the class of operation (e.g., Class A, B, or AB) oftransmitter 108. For example, enabling Class AB mode may reduce thecurrent drawn by transmitter 108, thereby further reducing the powerconsumption of transmitter 108, as compared to the first embodiment.Changing the bias of transmitter 108 from Class A or B mode to Class ABmode may reduce the power consumption of transmitter 108 by anadditional 25-40%, for example, as compared to the first embodiment.

According to a third embodiment, the power consumption of transmitter108 is reduced by connecting diode-connected transistors in parallel incurrent mirror 204. Current mirror 204 operates by providing a biascurrent I_(bias) in a ratio of M:1 to differential output terminals 104,where M is the number of diode-connected transistors coupled in parallelin transmitter 108. Thus, the current I flowing through transistor 218 emay be represented by the equation I=I_(bias)/M.

Second inputs 202 b gate the current I=I_(bias)/M across resistor 208.The output voltage of transmitter 108 is developed across resistor 208and provided to communication link 214 via center tapped transformer212. The output voltage is increased or decreased by adjusting thecurrent mirror ratio of M:1 that feeds resistor 208. In this embodiment,adding or subtracting diode-connected transistor(s) 216 in the referenceside of current mirror 204 adjusts the current I that flows throughresistor 208.

In FIG. 3, transmitter 108 includes diode-connected transistors 216 a-bthat are capable of being connected in parallel according to anembodiment of the present invention. The drain of diode-connectedtransistor 216 b is selectively connected to bias source 206, though thescope of the invention is not limited in this respect. For example,diode-connected transistors 216 a-b may be permanently coupled inparallel, meaning that transistors 216 a-b are “hard-wired” in parallel.In this example, transmitter 302 need not necessarily include switch302.

Referring to FIG. 3, switch 302 is shown in an open state forillustrative purposes. When switch 302 is open, diode-connectedtransistor 216 b is essentially an open-circuit. Thus, the current Pflowing through diode-connected transistor 216 a is equal to the currentprovided by bias source 206 (i.e., I′=I_(bias)).

Switch 302 may be closed to connect the drain of diode-connectedtransistor 216 b to bias source 206, thereby causing diode-connectedtransistors 216 a-b to be coupled in parallel. When switch 302 isclosed, the bias current I_(bias) is divided substantially evenlybetween diode-connected transistors 216 a-b, such that a currentI′=I_(bias)/2 flows through each diode-connected transistor 216 a-b. Thecurrent I′ is mirrored at transistor 218 e. Thus, the current flowingthrough transistor 218 e when switch 302 is closed may be represented asI=I′=I_(bias)/2.

By closing switch 302, diode-connected transistor 216 b is added to thereference side of current mirror 204, thereby reducing the currentmirror ratio to 2:1 so that the load current I is one-half of I_(bias).Reducing the load side current causes the output voltage across resistor208 to be reduced proportionally. Connecting diode-connected transistors216 in parallel reduces the power consumption of transmitter 108. Anynumber of diode-connected transistors 216 a-n may be added in parallel.

Referring to FIG. 3, switch 302 need not necessarily be coupled betweenthe drain of transistor 302 and bias source 206. For example, switch 302may be coupled between the gate of transistor 216 b and bias source 206or between the source of transistor 216 b and bias source 206.

Switch 302 may be controlled automatically or manually. For example,diode-connected transistor 216 b may be added to the reference side ofcurrent mirror 204 by automatically closing switch 302 when 1000 Base-Tmode is entered. Coupling diode-connected transistors 216 a-b inparallel may reduce the transmitter launch voltage and/or transmitterpower consumed during 1000 Base-T operation.

Transmitter 108 may be capable of switching to a lower output voltagewithout altering the signaling characteristics (e.g., pulse shape ormodulation rate) of transmitter 108. Elements, such as active hybrid210, may be configured to adjust to a lower transmit output voltage modeof transmitter 108. Enabling elements to adapt to the lower transmitoutput voltage mode may facilitate proper receive operation fortransmitter 108. Moreover, an element (e.g., active hybrid 210) mayreduce its cancellation voltage by a corresponding amount to facilitateproper cancellation of the transmitter voltage to be achieved at areceiver.

The transmit power of transmitter 108 may be successively reduced, basedon a series of detections performed by detection element 310. Forexample, the transmit power may be set at 50% of the standard transmitpower based on detection circuit 210 detecting 1000 base-T operation.The transmit power may be reduced from 50% of the standard transmitpower to 20% of the standard transmit power if another operatingcondition, such as a backplane application, is detected. The percentagesdescribed in this example are provided for illustrative purposes onlyand are not intended to limit the scope of the present invention. Thetransmit power of transmitter 108 may be set at any percentage of thestandard transmit power. Alternatively, the transmit power may be set tobe greater than the standard transmit power.

In FIG. 3, current mirror 204 includes two diode-connected transistors216 a-b for illustrative purposes, though current mirror 204 may includeany number of diode-connected transistors 216 a-b.

FIG. 4 shows transmitter 108 having three diode-connected transistors216 a-c that are capable of being connected in parallel according toanother embodiment of the present invention. In FIG. 4, switch 302 aselectively couples the drain of transistor 216 b to bias source 206,and switch 302 b selectively couples the drain of transistor 216 c tobias source 206. The drain of diode-connected transistor 216 a is shownto be hard-wired to bias source 206, though the scope of the presentinvention is not limited in this respect. For example, a switch may becoupled between the drain of diode-connected transistor 216 a and biassource 206 to enable diode-connected transistor 216 to be selectivelycoupled in parallel with one or more of transistors 216 b-c. Any ofdiode-connected transistors 216 a-c may be hard-wired or selectivelycoupled to bias source 206.

Referring to FIG. 4, switches 302 a-b are controlled to set the currentI that flows through transistor 218 e. In a first example, switches 302a-b are open, as shown in FIG. 4. In this example, the bias currentI_(bias) flows through transistor 216 a, and diode-connected transistors216 b-c are essentially open-circuits. Thus, I=I_(bias).

In a second example, switch 302 a is closed, and switch 302 b is open.The bias current I_(bias) is divided between diode-connected transistors216 a-b, such that a current of I′=I_(bias)/2 flows through each ofdiode-connected transistors 216 a-b.

In a third example, switch 302 a is open, and switch 302 b is closed.Half of the bias current I_(bias) flows through diode-connectedtransistor 216 a, and the other half of I_(bias) flows throughdiode-connected transistor 216 c, assuming that the gates ofdiode-connected transistors 216 a and 216 c have substantially the sameproportions. In this example, a current of I′=I_(bias)/2 flows througheach of diode-connected transistors 216 a and 216 c.

In a fourth example, switches 302 a-b are closed, thereby connectingrespective drains of diode-connected transistors 216 b-c to bias source206. The bias current I_(bias) is divided among diode-connectedtransistors 216 a-c, such that a current of I′=I_(bias)/3 flows througheach of diode-connected transistors 216 a-c. The current I flowingthrough transistor 218 e is mirrored from the reference side of currentmirror 204. Thus, the current I flowing through transistor 218 e may berepresented as I=I′=I_(bias)/3.

Coupling diode-connected transistors in parallel as described above withrespect to FIGS. 3 and 4 may substantially reduce the transmit power oftransmitter 108. For example, replacing one diode-connected transistorwith two diode-connected transistors coupled in parallel may reduce thetransmit power of transmitter 108 by approximately 50%. In anotherexample, replacing one diode-connected transistor with threediode-connected transistors coupled in parallel may reduce the powerconsumption by approximately 66.7%.

FIG. 5 illustrates a flowchart 500 of a method of operating atransmitter in accordance with an embodiment of the present invention.The invention, however, is not limited to the description provided bythe flowchart 500. Rather, it will be apparent to persons skilled in therelevant art(s) from the teachings provided herein that other functionalflows are within the scope and spirit of the present invention.

Flowchart 500 will be described with continued reference to exampletransmitter 108 described above in reference to FIGS. 2A-4, though themethod is not limited to those embodiments.

Referring now to FIG. 5, detection element 310 detects that a standardtransmit power is unnecessary at block 510. For example, detectionelement 310 may detect an operating condition associated withtransmitter 108 and/or communication link 214. The standard transmitpower is defined by a communication standard, such as 1000 base-T.Detection element may be implemented using hardware, software, orfirmware, or any combination thereof. Detection element 310 may detectthat the standard transmit power is unnecessary using any of a varietyof means. Detection element 310 may use a communication link diagnosticalgorithm, a programmable gain amplifier (PGA) setting, trial-and-error,or any other means.

A transmit power of transmitter 108 is set to be less than the standardtransmit power at block 520. The transmit power may be set by any of avariety of means. For example, center tap voltage 106 of transmitter 108may be set at a relatively low value by providing a relatively lowlaunch voltage for transmitter 108. A relatively low center tap voltagecorresponds with a relatively low transmitter power.

In another example, at least some elements 202-218 of transmitter 108are manipulated to change the class of operation of transmitter 108. Forinstance, the class of operation of transmitter 108 may be changed fromclass A or class B operation to class AB operation.

In yet another example, transmitter 108 includes a current mirror 204having a reference portion and a load portion. The reference portionincludes a plurality of diode-connected transistors 216 that areconnected in parallel. The reference portion is biased by a current thatis divided among the diode-connected transistors 216, thereby causingthe load portion of current mirror 204 to have a current that is lessthan the current that is provided to the reference portion of currentmirror 204.

According to an embodiment, the transmit power of transmitter 108 is setat approximately 50% of the standard transmit power in response todetecting a 1000 base-T protocol. In this embodiment, the transmit powercan be further reduced based another factor, such as the length ofcommunication link 214. For example, the transmit power may be furtherreduced to 20% or some other value less than 50% for backplaneapplications.

FIG. 7 illustrates a flowchart 700 of a method of operating atransmitter in accordance with another embodiment of the presentinvention. The invention, however, is not limited to the descriptionprovided by the flowchart 700. Rather, it will be apparent to personsskilled in the relevant art(s) from the teachings provided herein thatother functional flows are within the scope and spirit of the presentinvention.

Flowchart 700 will be described with continued reference to exampletransmitter 108 described above in reference to FIGS. 2A-4, though themethod is not limited to those embodiments.

Referring now to FIG. 7, a transmit power of transmitter 108 is set tobe less than the standard transmit power at block 710. The transmitpower may be set by any of a variety of means. For example, center tapvoltage 106 of transmitter 108 may be set at a relatively low value byproviding a relatively low launch voltage for transmitter 108. Inanother example, at least some elements 202-218 of transmitter 108 aremanipulated to change the class of operation of transmitter 108. In yetanother example, transmitter 108 includes a current mirror 204 having areference portion and a load portion, wherein the load portion has acurrent that is less than a current that is provided to the referenceportion. The transmit power of transmitter 108 may be set to be anyproportion of the standard transmit power.

At block 720, detection element 310 determines whether the transmitpower, which is set at block 710, is sufficient. The determination maybe based on any of a variety of factors. For example, detection element310 may determine whether the transmit power is sufficient based on anoperating condition associated with transmitter 108 and/or communicationlink 214. In another example, detection element 310 may determinewhether the transmit power is sufficient based on whether an elementproperly operates in response to receiving the transmit power. Detectionelement 310 may determine whether the transmit power is sufficient usingany of a variety of means. Detection element 310 may use a communicationlink diagnostic algorithm, a programmable gain amplifier (PGA) setting,trial-and-error, or any other means.

FIG. 6 illustrates a flowchart 600 of a method of operating atransmitter in accordance with yet another embodiment of the presentinvention. The invention, however, is not limited to the descriptionprovided by the flowchart 600. Rather, it will be apparent to personsskilled in the relevant art(s) from the teachings provided herein thatother functional flows are within the scope and spirit of the presentinvention.

Flowchart 600 will be described with continued reference to exampletransmitter 108 described above in reference to FIGS. 2A-4, though themethod is not limited to those embodiments.

Referring now to FIG. 6, detection element 310 determines a length ofcommunication link 214 at block 610. The launch voltage of transmitter108 is set at block 620, based on the length determined at block 610.The launch voltage may be set using any of a variety of means, such asany of those described above. For example, center tap voltage 106 may bereduced by reducing the current I in transmitter 108. In anotherexample, center tap voltage 106 may be set independently of the currentI.

In any of the embodiments described above, the transmit power oftransmitter 108 may be set manually or automatically. The invention isnot limited to the voltages or power levels mentioned herein. Othervoltages may be used to reduce the transmitter power more or less.Alternatively, the transmitter power may be raised.

The power consumption reduction techniques described above may be usedalone or in any combination. Other power consumption reductiontechniques may be used in combination with the techniques describedabove. Transmitter 108 may communicate to other components in a networkthat transmitter 108 has a transmit power that is less than a standardtransmit power.

III. Other Embodiments

According to an embodiment, current mirror 204 is included in adigital-to-analog converter (DAC). In another embodiment, transistors218 a-e are included in a current amplifier and/or a current buffer. Forexample, the transmit voltage of transmitter 108 may be adjusted bymanipulating the amplification of the current amplifier and/or thecurrent buffer.

IV. Conclusion

Example embodiments of the methods, systems, and components of thepresent invention have been described herein. As noted elsewhere, theseexample embodiments have been described for illustrative purposes only,and are not limiting. Other embodiments are possible and are covered bythe invention. Such other embodiments will be apparent to personsskilled in the relevant art(s) based on the teachings contained herein.Thus, the breadth and scope of the present invention should not belimited by any of the above described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A transmitter configured to operate in accordance with acommunication standard, the transmitter comprising: a detection circuitconfigured to determine if a power requirement of a communication linkis less than a current transmit power based on a length of thecommunication link; and an amplifier configured to amplify an outputsignal for transmission over the communication link, wherein theamplifier is configured to reduce the current transmit power of theamplified output signal if the power requirement of the communicationlink is less than the current transmit power.
 2. The transmitter ofclaim 1, wherein the amplifier comprises: a current mirror configured toprovide an adjustable current to a load of the amplifier, wherein theadjustable current is configured to be reduced if the power requirementof the communication link is less than the current transmit power. 3.The transmitter of claim 2, wherein the current mirror comprises: aplurality of diode-connected transistors.
 4. The transmitter of claim 1,wherein the amplifier is further configured to change a class ofoperation of the amplifier if the power requirement of the communicationlink is less than the current transmit power.
 5. The transmitter ofclaim 1, wherein the detection circuit is configured to determine if thelength of the communication link is less than a threshold value.
 6. Atransmitter configured to operate in accordance with a communicationstandard, comprising: a detection circuit configured to determine if apower requirement of a communication link is less than a currenttransmit power based on a current operation condition of thecommunication link; and an amplifier configured to amplify an outputsignal for transmission over the communication link, wherein theamplifier is configured to reduce the current transmit power of theamplified output signal if the power requirement of the communicationlink is less than the current transmit power.
 7. The transmitter ofclaim 6, wherein the amplifier comprises: a current mirror configured toprovide an adjustable current to a load of the amplifier, wherein theadjustable current is configured to be reduced if the power requirementof the communication link is less than the current transmit power. 8.The transmitter of claim 7, wherein the current mirror comprises: aplurality of diode-connected transistors.
 9. The transmitter of claim 6,wherein the amplifier is further configured to change a class ofoperation of the amplifier if the power requirement of the communicationlink is less than the current transmit power.
 10. The transmitter ofclaim 6, wherein the current operation condition of the communicationlink is at least one of a length of the communication link, anattenuation characteristic of the communication link, and asignal-to-noise ratio (SNR) associated with the communication link. 11.The transmitter of claim 6, wherein the detection circuit is configuredto determine if a length of the communication link is less than athreshold value.
 12. The transmitter of claim 6, wherein the detectioncircuit is configured to determine if an attenuation characteristic ofthe communication link does not exceed a threshold value.
 13. Thetransmitter of claim 6, wherein the detection circuit is configured todetermine if a signal-to-noise ratio (SNR) associated with thecommunication link exceeds a threshold value.
 14. A transmitterconfigured to operate in accordance with a communication standard, thetransmitter comprising: a detection circuit configured to perform aseries of detections to determine if a power requirement of acommunication link is less than a current transmit power; and anamplifier configured to amplify an output signal for transmission overthe communication link, wherein the amplifier is configured tosuccessively reduce the current transmit power of the amplified outputsignal, for each detection of the series of detections performed by thedetection circuit that determines the power requirement of thecommunication link is less than a current transmit power.
 15. Thetransmitter of claim 14, wherein the series of detections include atleast one of detecting a length of communication link, detecting anattenuation characteristic of the communication link, and detecting asignal-to-noise ratio (SNR) associated with the communication link. 16.The transmitter of claim 14, wherein the amplifier comprises: a currentmirror configured to provide an adjustable current to a load of theamplifier, wherein the adjustable current is configured to be reduced ifthe power requirement of the communication link is less than the currenttransmit power.
 17. The transmitter of claim 16, wherein the currentmirror comprises: a plurality of diode-connected transistors.
 18. Thetransmitter of claim 14, wherein the amplifier is further configured tochange a class of operation of the amplifier if the power requirement ofthe communication link is less than the current transmit power.